The invention relates to an SCR exhaust gas aftertreatment device which is particularly useful, e.g., for diesel motor internal combustion engines having a very large exhaust gas volume and/or divided exhaust gas trains.
Already known from DE 198 17 994 A1—first embodiment—is an exhaust gas aftertreatment device in which a pump pumps ammonia from an ammonia reservoir into a line and places it therein under constant pressure. Four metering valves open off the line. Each of these metering valves feeds the ammonia into the partial train of an exhaust gas manifold, which is assigned to a combustion compartment of an internal combustion engine. In this way, nitrogen oxides (NOx) will be reduced in the exhaust gas.
In its embodiment of FIG. 2A, DE 699 10 605 T2 relates to an SCR catalyst in which urea is fed directly in stages to the SCR catalyst by means of three metering valves, at the beginning, in the middle, and at the end.
DE 41 04 382 A1 relates to a gas turbine in which an aqueous ammonia solution is fed by means of three nozzles to points of various compression.
The unpublished DE 10 2008 012 780 relates to an SCR exhaust gas aftertreatment device in which a supply unit is employed together with a diaphragm pump and a pressure filter. Further provided is a metering unit, which has a pressure sensor, a valve, and an atomizer. As a reductant, an aqueous urea solution circulates in an open circuit. The open circuit, along with other measures, ensures that aqueous urea solution expanding below the freezing point cannot damage the SCR exhaust gas aftertreatment device. Provided in the metering unit in order to build up sufficient pressure at the valve for the atomizer, in spite of the open circuit, is a backflow restrictor.
The problem of the invention is to create a low-cost SCR exhaust gas aftertreatment device for internal combustion engines having very large exhaust gas volumes and/or divided exhaust gas trains.
This object is achieved in accordance with the invention by the features of patent claim 1.